Before you get too excited, NASA is NOT testing a planetary defense system against aliens. You know my feelings on this. I think it is dangerous to keep sending signals into space to attract the attention of extraterrestrials. We can't assume they are friendly. In case they are NOT, we better be ready.
But the purpose of the announcing testing of a planetary defense system by NASA is to try and knock an asteroid off course.
The space agency is teaming up with the European Space Agency to try to alter the course of "Diddymoon," one the size of the Great Pyramid around seven million miles away. It's not a threat to Earth (because who is afraid of an asteroid named "Diddymoon????"), but if an asteroid of similar size were to hit the planet it could cause some serious damage.
The first part of the plan involves launching a special probe, called DART, at the rock sometime in 2021, smashing into the target in 2022. The Europeans will then send a second probe to see how effective the test was. It would take far more power than the DART probe to deflect a massive asteroid headed toward Earth, but scientists say this test is an important first step.
Meanwhile, while we are shooting at space rocks, a military force of little green men prepare...